The present disclosure relates to assembly of structures with smoothly curved surfaces, and relates particularly to construction of hydrofoil shapes such as those of skegs for oceangoing barges.
Oceangoing barges can be towed more economically when equipped with hydrofoil skegs such as those disclosed in Gruzling, U.S. Pat. Nos. 4,217,844 and 4,569,302, and in Heyrman, et al., U.S. Pat. No. 4,782,779, than when not equipped with such skegs.
In the past, hydrofoil skegs for barges were manufactured in a highly labor-intensive manner, with skin plates for the skegs being cut oversized from plate material of the required thickness, and then bent to the required curved shape for the location of the skin. Thereafter, the bent skin plate was burned into three parts, a nose part, a middle part, and a tail part, and the edges of each part were then scarfed by hand so that a V-groove weld could be used to rejoin the parts of the skin plate during final assembly. Each skin plate part was welded to several supporting web members to form a structural section of the skeg, and girders were welded to the web members of the middle section. Finally, the nose and tail sections were welded to the middle section, which required numerous passes of hand welding to create the V-groove welds rejoining the sections of the skin parts for each side of the skeg, another multiple pass V-groove weld along the nose of the skeg, and welds along the tail edge of the skeg, to completely interconnect the skin plates of the opposite sides of the skeg to each other.
Cutting torches could be guided mechanically to follow lines scribed or drawn on the surface of the skin plate. For example, the cutting torch could be guided by tracks fastened to the metal being cut, but the tracks often shifted as a result of the heat distortion encountered during the burning process, but after being scarfed by hand the skin parts frequently did not meet closely when the structural sections were assembled, and gaps that resulted between the edges of the plate pieces were too deep to permit the plate sections to be simply welded together.
What is needed, then are methods by which to cut and bevel a plate to form parts of a skin for a skeg or hydrofoil more accurately than has been previously possible, and to assemble a hydrofoil structure more precisely, more quickly, and with less labor than was previously required for construction of such a hydrofoil structure.